Delirium is a common syndrome in older adults, characterized by a sudden and fluctuating decline in cognitive functioning. Most cases of delirium occur in older adults with dementia during an acute illness. Delirium superimposed on dementia (DSD) carries a high rate of morbidity and mortality and a national cost rivaling that of diabetes. DSD persists much longer in the post-hospital period than formerly recognized and accelerates the trajectory of cognitive decline. These older adults experience more complications, realize less rehabilitation potential and are at risk for premature institutionalization. Currently there are few evidence-based treatments for DSD. We have developed a theory-based intervention for DSD that is derived from the literature on cognitive reserve and based on our prior work. Both delirium and dementia are conditions of reduced cognitive reserve and share common risk factors: a lifetime of low engagement in complex mental activities and presence of the ApoE *E4 allele. Several lines of evidence also indicate that delirium and dementia share many clinical, metabolic, and cellular manifestations that indicate reduced cognitive reserve. It is plausible, then, that interventions that improve cognitive reserve in one condition may also be effective in the other. Cognitively stimulating activities improve cognitive functioning by inducing neuroplastic events that support cognitive reserve. Our clinical observations and preliminary work indicate that use of these activities may also help resolve DSD: individually tailored cognitive activities can facilitate processing in the cognitive domains affected by delirium: attention, orientation, memory, abstract thinking, and executive functioning. Cognitive processing helps restore cognitive functioning. In delirium, improved cognitive function is accompanied by improvement in physical function and resolution of delirium. Our primary aim in this RCT is to test the efficacy of Recreational Stimulation for Elders as a Vehicle to resolve DSD (RESERVE- DSD). We will randomize 256 subjects, newly admitted to post acute care, to intervention (RESERVE-DSD) or control (usual care). Intervention subjects will receive 30-minute sessions of tailored cognitively stimulating recreational activities for up to 30 days. We hypothesize that subjects who receive RESERVE-DSD will have: decreased severity and duration of delirium; greater gains in attention, orientation, memory, abstract thinking, and executive functioning; and greater gains in physical function compared to subjects with DSD who receive usual care. We will also evaluate potential moderators of intervention efficacy (lifetime of complex mental activities and APOE status). Our secondary aim is to describe the costs associated with RESERVE-DSD. This project builds on over a decade of funded research and clinical practice conducted by the investigators, and brings their unique and collaborative efforts together in an innovative manner to address the problem of DSD in post-acute care. PUBLIC HEALTH RELEVANCE: This research addresses a significant public health concern, accelerated mental and physical decline in people with dementia following an episode of delirium (acute confusion). There is evidence to suggest that this costly health issue can be addressed using individualized mentally stimulating activities.